Surgery – Respiratory method or device – Means placed in body opening to facilitate insertion of...
Reexamination Certificate
2002-04-30
2004-04-20
Lewis, Aaron J. (Department: 3761)
Surgery
Respiratory method or device
Means placed in body opening to facilitate insertion of...
C128S207140, C128S207160
Reexamination Certificate
active
06722362
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to an insufflation system and method, as well as an insufflation attachment for a ventilation system, that delivers a flow of insufflation gas to the airway of a patient to remove expired gases from a patient's anatomical dead space and/or the structural dead space in a breathing circuit during ventilation, and, in particular, to an insufflation system, method, and attachment in a ventilation system that delivers a flow of insufflation gas to the patient's airway in such a manner so as to minimize stagnation pressure in the patient's lungs due to the flow of insufflation gas into the patient and to an insufflation system, method and attachment that can be used in conjunction with a conventional ventilation system without altering the operation of the conventional ventilation system.
2. Description of the Related Art
It is known to reduce rebreathing of exhaled gases in an intubated patient or in a patient with a tracheostomy by providing a flow of insufflation gas, such as oxygen, an oxygen mixture, or other therapeutic gas, into the distal end of the patient's breathing circuit.
FIG. 1
illustrates an example of such a conventional system, commonly referred to as a tracheal gas insufflation (TGI) system, in which a flow of insufflation gas is delivered to the airway of the patient. A primary flow of breathing gas that augments or completely supports the patient's breathing is delivered using a conventional ventilator.
As shown in
FIG. 1
, an endotracheal tube
30
inserted into an airway
32
of a patient
34
through the oral cavity delivers the primary flow of breathing gas from a ventilator
36
to the patient's lungs
38
. In such a conventional ventilation system, a breathing circuit
40
delivers the primary flow of breathing gas from the ventilator to the patient via a first limb
42
, and exhaled gas from the patient is removed via a second limb
44
. First and second limbs
42
and
44
are typically flexible tubes coupled to endotracheal tube
30
via a coupling member, such as a Y-adapter. For purposes of this invention, the breathing circuit includes all of the structures associated with the ventilation system that communicate the primary flow of breathing gas with the airway of the patient, such as first limb
42
, second limb
44
, endotracheal tube
30
and any coupling members.
As the patient inspires, the primary flow of breathing gas is delivered by ventilator
36
to the patient's respiratory system, i.e., the airway and lungs, via breathing circuit
40
. Typically, the primary flow of gas delivered to the patient by the ventilator is controlled based on the total volume delivered, the pressure of the gas delivered, or the patient's respiratory effort, the latter of which is known as proportional assist ventilation (PAV). While an endotracheal tube, which is passed into the patient's airway via the oral cavity, is illustrated in
FIG. 1
as being part of the breathing circuit, it is to be understood that other methods for delivering and/or interfacing breathing gas to the patient, such as a tracheostomy tube, nasal and/or oral mask, or an nasal intubated endotracheal tube, are commonly used in conventional ventilation systems as part of the breathing circuit.
As the patient expires, i.e., breathes out, the exhaled gas, which is laden with CO
2
, is removed from the lungs and airway via endotracheal tube
30
and second limb
44
of breathing circuit
40
. Typically, an exhaust valve (not shown) associated with second limb
44
and operating under the control of ventilator
36
manages the flow of exhaust gas from the patient so that, if desired, a certain level of positive endexpiratory pressure (PEEP) can be maintained in the patient's respiratory system. In some ventilation systems, the second limb includes an exhaust valve that is controlled by the ventilator but is not contained within the ventilator itself.
It can be appreciated that at the end of exhalation, not all of the exhaled gas containing CO
2
, for example, is exhausted to atmosphere. A certain amount of exhaled gas remains in the physiological and anatomical dead space within the patient and in the structural dead space within the breathing circuit. The structural dead space in the breathing circuit is the portion of the breathing circuit beginning at a distal end
55
of endotracheal tube
30
or tracheostomy tube to a location
46
, where the exhalation (second) limb
44
separates from the rest of the breathing circuit. It is generally desirable to prevent the exhaled, CO
2
laden gas in this dead space from being rebreathed by the patient, so that the patient receives the maximum amount of oxygen or other therapeutic gas and a minimal amount of CO
2
during each breath. In some patients, such as patients with cranial injuries, it is imperative that their CO
2
level not be elevated.
Tracheal gas insufflation (TGI) is one method that attempts to remove the exhaled gas from the physiological, anatomical and structural dead spaces in a patient being treated with a ventilator. Tracheal gas insufflation involves introducing an insufflation gas, such as oxygen, an oxygen mixture, or other therapeutic gas, into the patient's airway
32
at the distal end of breathing circuit
40
. In the embodiment illustrated in
FIG. 1
, an insufflation gas source
48
, such as a pressurized tank or oxygen or an oxygen wall supply, delivers a flow of insufflation gas via a conduit
50
as a stream of gas into the patient's airway. Conduit
50
is also referred to as an “insufflation catheter.” In a conventional TGI system, a proximal end of conduit
50
is coupled to insufflation gas source
48
through a control valve
52
, and a distal end of conduit
50
is located generally within or near the distal end of endotracheal tube
30
so that the flow of insufflation gas is directed toward lungs
38
, as indicated by arrow
54
. Typically, the distal end of conduit
50
is located just above the patient's carina. The oxygen rich flow of insufflation gas discharged from the distal end of conduit
50
displaces the exhaled air in the anatomical and structural dead spaces so that the patient inhales the fresh (non CO
2
laden) gas on the next breath, thereby minimizing rebreathing of CO
2
to keep the patient's CO
2
levels as low a possible.
Conventionally, there are two techniques for delivering the flow of tracheal insufflation gas to a patient. According to a first TGI technique, the flow of insufflation gas is delivered to the patient continuously during the entire breathing cycle while the ventilator delivers the primary flow of breathing gas to the patient. This technique is commonly referred to as a “continuous TGI system.” This continuous TGI delivery method, however, has a significant drawback in that conventional ventilators are not capable of accounting for the additional volume of gas delivered to the patient by the continuous TGI system. As a result, the extra volume of gas bled into the breathing circuit by the continuous TGI system is simply summed with the prescribed volume of gas being delivered by the ventilator. A possible outcome is that an excessive pressure of gas is delivered to the patient, possibly over-inflating the patient's lungs. This excessive pressure is referred to as “autoPEEP.” A disadvantage associated with autoPEEP is that it increases the patient's work of breathing, because in order to initiate inspiration, the patient must generate an inhalation force that is strong enough to overcome the autoPEEP pressure. AutoPEEP may also cause tissue damage due to the hyper-inflation of the patient's lungs.
These problems are dealt with, at least in part, in conventional continuous TGI systems by carefully adjusting the ventilator settings to avoid over-inflation. It can be appreciated that “fooling” the ventilator so that the continuous flow of insufflation gas does not over-inflate the patient's respiratory syst
Hete Bernie
McCann Thomas A.
Haas Michael W.
Lewis Aaron J.
Respironics Inc.
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